Azo dyes for thermotransfer printing

ABSTRACT

Azo dyes useful for thermotransfer printing have the formula ##STR1## where the substituents have the following meanings: X is a radical of the formula IIa or IIb ##STR2## R 1  is H, C 1  -C 6  -alkyl or phenyl which may be substituted by C 1  -C 4  -alkyl, C 1  -C 2  -alkoxy, chlorine, bromine or cyano, 
     R 2  is H, C 1  -C 4  -alkyl, C 1  -C 4  -alkoxy, chlorine or bromine, n is 1 or 2, K is a radical of a coupling component II 
     
         H--K                                                       III 
    
      of the aniline, aminonaphthaline, pyrazole, diaminopyridine, hydroxypyridone or tetrahydroquinoline series.

The present invention relates to the use in thermotransfer printing ofazo dyes of the formula I ##STR3## where the substituents have thefollowing meanings: X is a radical of the formula IIa or IIb ##STR4##where R₁ is hydrogen, C₁ -C₆ -alkyl, or phenyl which may be substitutedby C₁ -C₄ -alkyl, C₁ -C₂ -alkoxy, chlorine, bromine or cyano,

n is 1 or 2, and

R² is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, chlorine or bromine, and

K is the radical of a coupling component III

    H--K                                                       III

of the aniline, aminonapthaline, pyrazole, diaminopyridine,hydroxypyridone or tetrahydroquinoline series

and specifically to a process for transferring these azo dyes bydiffusion from a transfer to a plastic-coated substrate with the aid ofa thermal printing head.

The technique of thermotransfer printing is common knowledge; suitableheat sources besides lasers and IR lamps are in particular thermalprinting heads capable of emitting short heat pulses lasting fractionsof a second.

In this preferred embodiment of thermotransfer printing, a transfersheet which contains the transfer dye together with one or more binders,a support material and possibly further assistants such as releaseagents or crystallization inhibitors is heated from the back with thethermal printing head, causing the dye to migrate out of the transfersheet and to diffuse into the surface coating of the substrate, forexample into the plastic coat of a coated sheet of paper.

The essential advantage of this process is that the amount of dye to betransferred (and hence the color gradation) can be controlled in aspecific manner via the amount of energy supplied to the thermalprinting head.

Thermal transfer printing is in general carried out using the threesubtractive primaries yellow, magenta and cyan (with or without black),and the dyes used must have the following properties to ensure optimalcolor recording: ready thermal transferability, little tendency tomigrate within or out of the surface coating of the receiving medium atroom temperature, high thermal and photochemical stability, and alsoresistance to moisture and chemicals, no tendency to crystallize onstorage of the transfer sheet, a suitable hue for subtractive colormixing, a high molar absorption coefficient, and ready industrialavailability.

It is very difficult to meet all these requirements at one and the sametime. In particular, the magenta dyes used to date have not been fullysatisfactory. This is also true for example of the azo dyes described,and recommended for thermal transfer, in U.S. Pat. No. 4,764,178, whichhave coupling components based on aniline, tetrahydroquinoline,aminoquinoline or julolidine, and also of the azo dyes known fromEP-A-258,856 and U.S. Pat. No. 4,698,651 for the same purpose which havecoupling components based on aniline, these dyes differing from the azodyes I inter alia by the nature of the substituent in the thiazole ringwhich is ortho to the nitrogen atom.

The azo dyes I themselves are known from earlier German PatentApplications P 38 10 643.4 and P 38 16 698.4 or can be obtained by themethods mentioned therein.

It is an object of the present invention to find suitable red and yellowdyes for thermotransfer printing which come closer to the requiredproperty profile than the prior art dyes.

We have found that this object is achieved by the azo dyes I defined atthe beginning.

We have also found a process for transferring azo dyes by diffusion froma transfer to a plastic-coated substrate with the aid of a thermalprinting head, which comprises using for this purpose a transfer onwhich are situated one or more of the azo dyes I defined at thebeginning.

Suitable alkyl R¹ or R² is in particular methyl, ethyl, propyl,isopropyl, butyl, isobutyl, sec-butyl or tert-butyl. Alkyl R¹ may alsobe pentyl, isopentyl, neopentyl, tert-pentyl, hexyl or 2-methylpentyl.

Alkoxy R² is for example methoxy, ethoxy, propoxy, isopropoxy, butoxy orisobutoxy.

Substituted phenyl R¹ is for example methylphenyl, ethylphenyl,methoxyphenyl, ethoxyphenyl, chlorophenyl, bromophenyl or cyanophenyl,in each of which the substituents are in position 2, 3 or 4.

Preferred X of the formula IIa or IIb is for example:

Methoxymethyl, ethoxymethyl, propoxymethyl, butoxymethyl,2-methoxyethyl, 2-ethoxyethyl, 2-propoxyethyl, 2-butoxyethyl,2-pentyloxyethyl, 2-hexyloxyethyl, or 2-, 3- or 4-pyridyl.

Preferred coupling components III are:

aniline derivatives of formula IIIa ##STR5## aminonaphthalinederivatives of the formula IIIb ##STR6## pyrazole derivatives of theformula IIIc ##STR7## diaminopyridine derivatives of the formula IIId##STR8## hydroxypyridone derivatives of the formula IIIe ##STR9##tetrahydroquinoline derivatives of the formula IIIf ##STR10##

Here the substituents have the following meanings:

R³, R^(3'), R⁴ and R^(4') are each hydrogen;

C₁ -C₁₀ -alkyl whose carbon chain may be interrupted by from one tothree oxygen atoms in ether function and which may bear the followingsubstituents: cyano, hydroxyl, phenyl, phenoxy, phenylaminocarbonyloxy,benzyloxy, benzoyloxy, which may have C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy,fluorine, chlorine or bromine as substituents, C₁ -C₄ -alkanoyloxy, C₁-C₆ -alkoxycarbonyloxy, C₁ -C₈ -alkoxycarbonyl, mono- or di-C₁ -C₈-alkylaminocarbonyloxy, in the last three of which the carbon chain maybe interrupted by one or two oxygen atoms in ether function;

C₃ -C₅ -alkenyl or C₅ -C₇ -cycloalkyl; phenyl which may be substitutedby C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, C₁ -C₄ -dialkylamino, acetylamino,fluorine, chlorine or bromine;

R⁵ is hydrogen; chlorine;

C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, C₁ -C₄ -alkanoylamino, which may have C₁-C₄ -alkoxy, phenoxy or chlorine as substituents, C₂ -C₃ -alkenoylamino,benzoylamino, ureido, mono- or di-C₁ -C₄ -alkylureido or C₁ -C₄-alkylsulfonylamino;

R⁶ is hydrogen, chlorine, C₁ -C₄ -alkyl or C₁ -C₄ -alkoxy;

R⁷ is hydrogen, C₁ -C₈ -alkyl or phenyl;

R⁸ is hydrogen, C₁ -C₈ -alkyl, which may have phenyl, furyl or thienylas substituents, C₅ -C₇ -cycloalkyl or phenyl.

Suitable alkyl R³, R^(3'), R⁴, R^(4'), R⁵, R⁶, R⁷ or R⁸ is in particularmethyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl andtert-butyl.

Alkyls R³, R^(3'), R⁴, R^(4'), R⁷ and R⁸ may each also be for examplepentyl, isopentyl, neopentyl, tert-pentyl, hexyl, 2-methylpentyl,heptyl, octyl and 2-ethylhexyl, while R³, R^(3'), R⁴ and R^(4') may eachadditionally be for example nonyl or decyl.

If the carbon chain of alkyl R³, R^(3'), R⁴ or R^(4') is interrupted byfrom one to three oxygen atoms, it may be for example: 2-methoxyethyl,2-ethoxyethyl, 2-propoxyethyl, 2-butoxyethyl, 2- or 3-methoxypropyl,1-methoxy-2-propyl, 2-ethoxypropyl, 2-propoxypropyl, 4,7-dioxaoctyl,4,7-dioxanonyl, 4,8-dioxadecyl, 4,7,10-trioxaundecyl or4,7,10-trioxadodecyl.

Alkyl R³, R^(3'), R⁴ or R^(4') may additionally have cyano and hydroxylas substituents; corresponding examples are:

cyanomethyl, 2-cyanoethyl and 3-cyanopropyl, 2-hydroxyethyl,2-hydroxypropyl, 1-hydroxyprop-2-yl, 2-hydroxybutyl, 1-hydroxybut-2-yl,4-hydroxybutyl and 8-hydroxy-4-oxaoctyl.

Other suitable alkyls R³, R^(3'), R⁴ and R^(4') have phenyl, phenoxy,phenylaminocarbonyloxy and also benzyloxy or benzoyloxy as substituents,for example:

benzyl, 1-phenylethyl, 2-phenylethyl, 2-phenoxyethyl,6-phenoxy-4-oxahexyl, 2-(phenylaminocarbonyloxy)ethyl,

3-benzyloxypropyl, 2-benzoyloxyethyl, 2-(2-methylbenzoyloxy)ethyl,2-(4-methylbenzoyloxy)ethyl, 2-(4-chlorobenzoyloxy)ethyl,2-(4-methoxybenzoyloxy)ethyl, 2-benzoyloxypropyl or 2-benzyloxybutyl.

If alkyl R³, R^(3'), R⁴ or R^(4') is substituted by alkanoyloxy,alkoxycarbonyloxy, alkoxycarbonyl or alkylaminocarbonyloxy, theresulting groups are for example:

2-acetyloxyethyl, 2-propionyloxyethyl, 2-pentanoyloxyethyl,2-acetyloxypropyl, 3-acetyloxypropyl, 2-propionyloxypropyl,2-acetyloxybutyl, 4-acetyloxybutyl, 2-propionyloxybutyl and8-acetyloxy-4-oxaoctyl;

2-(ethoxycarbonyloxy)ethyl, 2-(butoxycarbonyloxy)ethyl and4-(ethoxycarbonyloxy)butyl;

methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl,butoxycarbonylmethyl, 1-(methoxycarbonyl)ethyl,2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl,2-(propoxycarbonyl)ethyl, 2-(butoxycarbonyl)ethyl,2-(isobutoxycarbonyl)ethyl, 2-(2-ethylhexyloxycarbonyl)ethyl,2-(3-oxabutyloxycarbonyl)ethyl, 2-(3-oxapentyloxycarbonyl)ethyl and2-(3-oxaheptyloxycarbonyl)ethyl;

2-(diethylaminocarbonyloxy)ethyl.

Alkenyl, cycloalkyl or substituted phenyl R³, R^(3'), R⁴ or R^(4') isfor example:

allyl or methallyl;

cyclopentyl, cyclohexyl, methylcyclohexyl or cycloheptyl; 2-, 3- or4-methylphenyl, 2- or 4-methoxyphenyl, 2- or 4-ethoxyphenyl,4-dimethylaminophenyl, 4-acetylaminophenyl, 5-chlorophenyl or2,4-dichlorophenyl.

Suitable alkoxy R⁵ or R⁶ is for example methoxy, ethoxy, propoxy,isopropoxy, butoxy or isobutoxy.

R⁵ can also be for example alkanoylamino, alkenoylamino, benzoylamino,alkylureido or alkylsulfonylamino, such as:

acetylamino, propionylamino, methoxyacetylamino, ethoxyacetylamino,chloroacetylamino, phenoxyacetylamino;

acryloylamino or methacryloylamino; N-methylureido, N-butylureido orN,N-dimethylureido; methylsulfonylamino, ethylsulfonylamino,propylsulfonylamino or butylsulfonylamino.

R⁸ can also be for example substituted alkyl such as benzyl, 1- or2-phenylethyl, 2-furylmethyl, 2-(2-furyl)ethyl, 2-(2-thienyl)ethyl or2-(2-pyridyl)ethyl.

Of the abovementioned coupling components H-K, those of the formulaeIIIa, IIIc, IIId, IIIe and IIIf are particularly preferred.

Very particularly preferred coupling components are aniline derivativesIIIa and tetrahydroquinoline derivatives IIIf where the substituentshave the following meanings:

R³ and R⁴ are each hydrogen;

C₁ -C₈ -alkyl whose carbon chain may be interrupted by an oxygen atomand which may carry cyano, hydroxyl, C₁ -C₄ -alkanoyloxy or C₁ -C₈-alkoxycarbonyl as substituents; or C₅ -C₇ -cycloalkyl;

R⁵ is hydrogen, methyl, methoxy or acetylamino;

R⁶ is hydrogen; and

R⁷ is methyl.

Preferred azo dyes I may be discerned in the Examples.

The dyes I to be used according to the present invention are notable forthe following properties compared with prior art red and bluethermotransfer printing dyes: readier thermal transferability in spiteof the higher molecular weight, improved migration properties in thereceiving medium at room temperature, higher thermal stability, higherlightfastness, better resistance to moisture and chemicals, bettersolubility in printing ink preparation, higher color strength, andreadier industrial accessability.

In addition, the azo dyes I exhibit a distinctly better purity of hue,in particular in mixtures of dyes, and produce improved black prints.

The transfer sheets required as dye donors for the thermotransferprinting process according to the present invention are prepared asfollows. The azo dyes I are incorporated in an organic solvent, such asisobutanol, methyl ethyl ketone, methylene chloride, chlorobenzene,toluene, tetrahydrofuran or a mixture thereof, together with one or morebinders and possibly further assistants such as release agents orcrystallization inhibitors to form a printing ink in which the dyes arepreferably present in a molecularly dispersed, ie. dissolved, form. Theprinting ink is then applied to an inert support and dried.

Suitable binders for the use of the azo dyes I according to the presentinvention are all materials which are soluble in organic solvents andwhich are known to be suitable for thermotransfer printing, eg.cellulose derivatives such as methylcellulose, hydroxypropylcellulose,cellulose acetate or cellulose acetobutyrate, but in particularethylcellulose and ethylhydroxyethylcellulose, starch, alginates, alkydresins and vinyl resins such as polyvinyl alcohol orpolyvinylpyrrolidone but in particular polyvinyl acetate and polyvinylbutyrate. It is also possible to use polymers and copolymers ofacrylates and derivatives thereof, such as polyacrylic acid, polymethylmethacrylate or styrene/acrylate copolymers, polyester resins, polyamideresins, polyurethane resins or natural resins such as gum arabic.

It is frequently advisable to use mixtures of these binders, for examplemixtures of ethylcellulose and polyvinyl butyrate in a weight ratio of 2: 1.

The weight ratio of binder to dye is in general from 8 : 1 to 1 : 1,preferably from 5 : 1 to 2 : 1.

Suitable assistants are for example release agents based onperfluorinated alkylsulfonamidoalkyl esters or silicones as described inEP-A-227,092 and EP-A-192,435, and in particular organic additives whichstop the transfer dyes from crystallizing out in the course of storageor heating of the inked ribbon, for example cholesterol or vanillin.

Inert support materials are for example tissue, blotting or parchmentpaper and films made of heat resistant plastics such as polyesters,polyamides or polyimides, which films may also be metal coated.

The inert support may additionally be coated on the side facing thethermal printing head with a lubricant in order that adhesion of thethermal printing head to the support material may be prevented. Suitablelubricants are for example silicones or polyurethanes as described inEP-A-216,483.

The thickness of the support is in general from 3 to 30 μm, preferablyfrom 5 to 10 μm.

The substrate to be printed, eg. paper, must in turn be coated with abinder which receives the dye during the printing process. It ispreferable to use for this purpose polymeric materials whose glasstransition temperatures T_(g) are within the range from 50° to 100° C.,eg. polycarbonates and polyesters. Details may be found in EP-A-227,094,EP-A-133,012, EP-A-133,011, JP-A-199,997/1986 or JP-A-283,595/1986.

The process according to the present invention is carried out using athermal printing head which is heatable to above 300° C., so that dyetransfer takes not more than 15 msec.

EXAMPLES

First, transfer sheets (donors) were produced in a conventional mannerfrom a polyester sheet 8 μm in thickness coated with an approximately 5μm thick transfer layer of a binder B which in each case contained about0.25 g of azo dye I. The weight ratio of binder to dye was in each case4 : 1.

The substrate (receiver) to be printed was paper about 120 μm inthickness which had been coated with a layer of plastic 8 μm inthickness (Hitachi Color Video Print Paper).

Donor and receiver were placed on top of one another with the coatedfronts next to each other then wrapped in aluminum foil and heatedbetween two hotplates at 70°-80° C. for 2 minutes. This operation wasrepeated three times with similar samples at a temperature within therange from 80° to 120° C., the temperature being increased each time.

The amount of dye diffusing into the plastics layer of the receiver inthe course of transfer is proportional to the optical density determinedphotometrically as absorbance A after each heating phase at theabovementioned temperatures.

The plot of the logarithm of the measured absorbances A against thecorresponding reciprocal of the absolute temperature is a straight linefrom whose slope it is possible to calculate the activation energyΔE_(T) for the transfer experiment: ##EQU1##

From the plot it is additionally possible to discern the temperature T*at which the absorbance attains the value 2, ie. at which thetransmitted light intensity is one hundredth of the incident lightintensity. The lower the temperature T*, the better the thermaltransferability of the particular dye.

Tables la to 9a list the azo dyes I which were studied in respect oftheir thermal transfer characteristics together with their hues.

The related Tables 1b to 9b list the particular binder B used employingthe following abbreviations: EC=ethylcellulose, PVB=polyvinyl butyrate,MIX=EC:PVB=2:1, EHEC=ethylhydroxyethylcellulose, CA=cellulose acetate)and the previously mentioned parameters T* [°C.]and ΔE_(T) [kcal/mol].

                                      TABLE 1a                                    __________________________________________________________________________     ##STR11##                                                  IIIa              Ex.                                                                              R.sup.1                                                                           n R.sup.3            R.sup.4      R.sup.5  R.sup.6                                                                             Hue                   __________________________________________________________________________     1 CH.sub.3                                                                          2 C.sub.4 H.sub.9    CH(CH.sub.3)C.sub.2 H.sub.5                                                                NHCOCH.sub.3                                                                           H     violet                 2 CH.sub.3                                                                          2 C.sub.3 H.sub.7    C.sub.3 H.sub.7                                                                            NHCOCH.sub.3                                                                           H     violet                 3 CH.sub.3                                                                          2 C.sub.6 H.sub.13   C.sub.2 H.sub.5                                                                            OCH.sub.3                                                                              H     violet                 4 CH.sub.3                                                                          2 H                  C.sub.4 H.sub.9                                                                            CH.sub.3 OCH.sub.3                                                                           violet                 5 CH.sub.3                                                                          2 C.sub.2 H.sub.5    C.sub.2 H.sub.5                                                                            H        H     violet                 6 CH.sub.3                                                                          2 (CH.sub.2).sub.2 OCH.sub.3                                                                       (CH.sub.2).sub.2 OCH.sub.3                                                                 H        H     violet                 7 CH.sub.3                                                                          2 (CH.sub.2).sub.2 OCOCH.sub.3                                                                     (CH.sub.2).sub.2 OCOCH.sub.3                                                               CH.sub.3 H     bluish red             8 CH.sub.3                                                                          2 (CH.sub.2).sub.2 Ph                                                                              (CH.sub.2).sub.2 CN                                                                        H        H     red                    9 CH.sub.3                                                                          2 (CH.sub.2).sub.2 OCOC.sub.2 H.sub.5                                                              (CH.sub.2).sub.2 OCOC.sub.2 H.sub.5                                                        Cl       H     red                   10 CH.sub.3                                                                          2 (CH.sub.2).sub.2 OCOC.sub.2 H.sub.5                                                              (CH.sub.2).sub.2 CN                                                                        H        H     red                   11 CH.sub.3                                                                          2 (CH.sub.2).sub.2 CN                                                                              (CH.sub.2 CHCH.sub.2                                                                       H        H     red                   12 CH.sub.3                                                                          2 (CH.sub.2).sub.2 OCOCH.sub.3                                                                     (CH.sub.2).sub. 2 OCOCH.sub.3                                                              CH.sub.3 OCH.sub.3                                                                           violet                13 CH.sub.3                                                                          2 CH.sub.2 CHCH.sub.2                                                                              CH.sub.2 CHCH.sub.2                                                                        NHCOCH.sub.3                                                                           OCH.sub.3                                                                           reddish blue          14 CH.sub.3                                                                          2 (CH.sub.2).sub.2 COO(CH.sub.2).sub.2 OC.sub.2 H.sub.5                                            C.sub.2 H.sub.5                                                                            H        H     red                   15 CH.sub.3                                                                          2 (CH.sub.2).sub.2 CN                                                                              C.sub.2 H.sub.5                                                                            CH.sub.3 H     bluish red            16 CH.sub.3                                                                          2 (CH.sub.2).sub.2 COOCH.sub.3                                                                     C.sub.2 H.sub.5                                                                            H        H     red                   17 CH.sub.3                                                                          2 (CH.sub.2).sub.2 OH                                                                              C.sub.4 H.sub.9                                                                            CH.sub.3 H     violet                18 CH.sub.3                                                                          2 C.sub.2 H.sub.5    C.sub.2 H.sub.5                                                                            NHCOCH.sub.3                                                                           H     violet                19 CH.sub.3                                                                          2 (CH.sub.2).sub.2 OCOCH.sub.3                                                                     C.sub.2 H.sub.5                                                                            CH.sub.3 H     violet                20  CH.sub.3                                                                         2 (CH.sub.2).sub.2 OCOCH.sub.3                                                                     (CH.sub.2).sub.2 OCOCH.sub.3                                                               H        H     red                   21 C.sub.2 H.sub.5                                                                   2 (CH.sub.2).sub.2 CN                                                                              C.sub.2 H.sub.5                                                                            CH.sub.3 H     bluish red            22 C.sub.2 H.sub.5                                                                   2 CH.sub.2Ph         (CH.sub.2).sub.2 COOCH.sub.3                                                               H        H     red                   23 C.sub.2 H.sub.5                                                                   2 C.sub.2 H.sub.5    C.sub.2 H.sub.5                                                                            H        H     violet                24 C.sub.4 H.sub.9                                                                   2 C.sub.2 H.sub.5    C.sub.2 H.sub.5                                                                            H        H     red                   25 CH.sub.3                                                                          1 (CH.sub.2).sub.2 CN                                                                              C.sub.2 H.sub.5                                                                            CH.sub.3 H     bluish red            26 CH.sub.3                                                                          1 (CH.sub.2).sub.2 COOCH.sub.3                                                                     C.sub.2 H.sub.5                                                                            H        H     red                   27 CH.sub.3                                                                          1 (CH.sub.2).sub.2 OH                                                                              C.sub.4 H.sub.9                                                                            CH.sub.3 H     violet                28 C.sub.4 H.sub.9                                                                   2 C.sub.2 H.sub.5    C.sub.2 H.sub.5                                                                            NHCOCH.sub.3                                                                           H     violet                29 C.sub.4 H.sub.9                                                                   2 (CH.sub.2).sub.2 OCOCH.sub.3                                                                     C.sub.2 H.sub.5                                                                            CH.sub.3 H     violet                30 C.sub.4 H.sub.9                                                                   2 (CH.sub.2).sub.2 OCOCH.sub.3                                                                     (CH.sub.2)OCOCH.sub.3                                                                      H        H     red                   31 C.sub.4 H.sub.9                                                                   2 C.sub.4 H.sub.9    (CH.sub.2).sub.2 CN                                                                        H        H     red                   32 C.sub.4 H.sub.9                                                                   2 CH.sub.2Ph         (CH.sub.2).sub.2 COOC.sub.4 H.sub.9                                                        H        H     red                   __________________________________________________________________________

                  TABLE 2a                                                        ______________________________________                                         ##STR12##                    IIIc                                            Ex.  R.sup.1  R.sup.7 R.sup.8    Hue                                          ______________________________________                                        33   CH.sub.3 H       Cyclohexyl yellowish orange                             34   CH.sub.3 H       Ph         yellowish orange                             35   CH.sub.3 H       Fur-2-ylmethyl                                                                           yellowish orange                             36   CH.sub.3 CH.sub.3                                                                              Ph         yellowish orange                             37   C.sub.2 H.sub.5                                                                        H       CH.sub.2Ph yellowish orange                             38   C.sub.2 H.sub.5                                                                        H       Cyclohexyl yellowish orange                             39   C.sub.4 H.sub.9                                                                        H       Cyclohexyl yellowish orange                             40   C.sub.4 H.sub.9                                                                        H       Ph         yellowish orange                             41   C.sub.4 H.sub.9                                                                        CH.sub.3                                                                              Fur-2-ylmethyl                                                                           yellowish orange                             ______________________________________                                    

    TABLE 3a      ##STR13##      IIId  Ex. R.sup.1 n R.sup.3      ' R.sup.3 R.sup.4 Hue                         42 CH.sub.3 2 H H     (CH.sub.2).sub.3O(CH.sub.2).sub.2OCH.sub.3 reddish orange 43 C.sub.2     H.sub.5 2 H H (CH.sub.2).sub.3O(CH.sub.2).sub.2OC.sub.2 H.sub.5 reddish     orange 44 CH.sub.3 2 H H (CH.sub.2).sub.3O[(CH.sub.2).sub.2O].sub.2C.sub.     2      H.sub.5 reddish orange 45 CH.sub.3 2 H H (CH.sub.2).sub. 3O(CH.sub.2).su     b.4OCOCH.sub.3 reddish orange 46 CH.sub.3 2 (CH.sub.2).sub.3 OCH.sub.3     (CH.sub.2).sub.2 OCH.sub.3 (CH.sub.2).sub.2OCH.sub.3 red 47 CH.sub.3 2     CH(C.sub.2 H.sub.5)CH.sub.2 OCOCH.sub.3 (CH.sub.2).sub.2 OCH.sub.3     (CH.sub.2).sub.2OCH.sub.3 red 48 CH.sub.3 2 (CH.sub.2).sub.3 OCH.sub.3     (CH.sub.2).sub.2 OCOCH.sub.3 C.sub.2 H.sub.5 red 49 C.sub.2 H.sub.5 2     (CH.sub.2).sub.3 O(CH.sub.2).sub.2 OCH.sub.3 H H reddish orange 50     CH.sub.3 2 (CH.sub.2).sub.3 O[(CH.sub.2).sub.2 O].sub.2 C.sub.2 H.sub.5     H H reddish orange 51 CH.sub.3 2 (CH.sub.2).sub.3 O[(CH.sub.2).sub.2     O].sub.2 C.sub.2 H.sub.5 (CH.sub.2).sub. 3 OCH.sub.3 H red 52 CH.sub.3 2 (     CH.sub.2).sub.3 O[(CH.sub.2).sub.2 O].sub.2 CH.sub.3 Ph H pink 53     CH.sub.3 2 (CH.sub.2).sub.3 O[(CH.sub.2).sub.2 O].sub.2 CH.sub.3     Ph-2-OCH.sub.3 H pink 54 CH.sub.3 2 C.sub.2 H.sub.5 (CH.sub.2).sub.3     O[(CH.sub.2).sub.2 O].sub.2 CH.sub.3 H red 55 CH.sub.3 2 C.sub.2 H.sub.5 (     CH.sub.2).sub.3 O(CH.sub.2).sub.4 OH H red 56 C.sub.4      H.sub.9 2 (CH.sub.2).sub.2 OCH.sub.3 (CH.sub.2).sub.3 O(CH.sub.2).sub.4 O     H H red 57 CH.sub.3 2 (CH.sub.2).sub.3 OCH.sub.3 (CH.sub.2).sub.3     O(CH.sub.2).sub.4 OH H red 58 CH.sub.3 2 (CH.sub.2).sub.3 O COCH.sub.3     (CH.sub.2).sub.3 O(CH.sub.2).sub.2 OC.sub.2 H.sub.5 H red 59 CH.sub.3 2     C.sub.2 H.sub.5 (CH.sub.2).sub.2 OCH.sub.3 (CH.sub.2).sub.2OCH.sub.3 red     60 CH.sub.3 2 (CH.sub.2).sub.3 O(CH.sub.2).sub.2      OCH.sub.3 Ph-2-OCH.sub.3 H red 61 CH.sub.3 2 (CH.sub.2).sub.2 OCH.sub.3 (     CH.sub.2).sub.2 OCH.sub.3 H red 62 C.sub.2                               O    (      H.sub.5 2 H H (CH.sub.2).sub.3CH.sub.2).sub.2OCH.sub.3 reddish orange     63 CH.sub.3 1 H H (CH.sub.2).sub.3O(CH.sub.2).sub.2OC.sub.2 H.sub.5     reddish orange 64 C.sub.4      H.sub.9 2 H H (CH.sub.2).sub.3O](CH.sub.2).sub.2O].sub.2C.sub.2 H.sub.5     reddish orange 65 C.sub.3      H.sub.7 2 H H (CH.sub. 2).sub.3O(CH.sub.2).sub.4OCOCH.sub.3 reddish     orange 66 C.sub.2 H.sub.5 1 (CH.sub.2).sub.3 OCH.sub.3 (CH.sub.2).sub.2  C     OH.sub.3 (CH.sub.2).sub.2OCH.sub.3 red 67 CH.sub.3 1 CH(C.sub.2      H.sub.5)CH.sub.2 OCOCH.sub.3 (CH.sub.2).sub.2                           O    C      OCH.sub.3 (CH.sub.2).sub.2H.sub.3 red 68 C.sub.4      H.sub.9 2 (CH.sub.2).sub.3 OCH.sub.3 (CH.sub.2).sub.2 OCOCH.sub.3     C.sub.2 H.sub.5 red 69 C.sub.4 H.sub.9 2 (CH.sub.2).sub.3      O(CH.sub.2).sub.2 OPh (CH.sub.2).sub.2      OCH.sub.3 (CH.sub.2).sub.2OCH.sub.3 red

                  TABLE 4a                                                        ______________________________________                                         ##STR14##                    IIIe                                            Ex.   R.sup.1  R.sup.3              Hue                                       ______________________________________                                        70    CH.sub.3 C.sub.2 H.sub.5      yellow                                    71    CH.sub.3 C.sub.4 H.sub.9      yellow                                    72    CH.sub.3 (CH.sub.2).sub.3 O(CH.sub.2).sub.2 OPh                                                             yellow                                    ______________________________________                                    

                                      TABLE 5a                                    __________________________________________________________________________     ##STR15##                               IIIf                                 Ex.                                                                              R.sup.1                                                                            n R.sup.3         R.sup.5     Hue                                     __________________________________________________________________________    73 CH.sub.3                                                                           2 C.sub.2 H.sub.5 H           violet                                  74 C.sub.2 H.sub.5                                                                    2 C.sub.3 H.sub.7 H           violet                                  75 CH.sub.3                                                                           2 C.sub.4 H.sub.9 CH.sub.3    violet                                  76 CH.sub.3                                                                           2 (CH.sub.2).sub.2 OC.sub.4 H.sub.9                                                             NHCOCH.sub.3                                                                              violet                                  77 C.sub.4 H.sub.9                                                                    1 C.sub.2 H.sub.5 CH.sub.3    violet                                  78 CH.sub.3                                                                           2 (CH.sub.2).sub.2 OCH.sub.3                                                                    H           violet                                  79 C.sub.4 H.sub.9                                                                    2 C.sub.2 H.sub. 5                                                                              H           violet                                  80 CH.sub.3                                                                           2 H               H           bluish red                              81 C.sub.6 H.sub.13                                                                   2 C.sub.4 H.sub.9 CH.sub.3    violet                                  82 CH.sub.3                                                                           2 (CH.sub.2).sub.2 COOCH.sub.2 OH                                                               CH.sub.3    violet                                  83 C.sub.2 H.sub.5                                                                    1 (CH.sub.2).sub.2 CN                                                                           NHCOCH.sub.3                                                                              violet                                  84 CH.sub.3                                                                           1 CH.sub.2 O(CH.sub.2).sub.2 OPh                                                                NHCOCH.sub.3                                                                              violet                                  85 CH.sub.3                                                                           1 C.sub.2 H.sub.5 NHSOOC.sub.4 H.sub.9                                                                      violet                                  86 C.sub.2 H.sub.5                                                                    2 (CH.sub.2).sub.2 OCOC.sub.6 H.sub.13                                                          NHSOOC.sub.2 H.sub.5                                                                      violet                                  87 CH.sub.3                                                                           1 (CH.sub.2).sub.2 OCOC.sub.3 H.sub.7                                                           NHCOC.sub.4 H.sub.9                                                                       violet                                  __________________________________________________________________________

                                      TABLE 6a                                    __________________________________________________________________________     ##STR16##                                                  IIIa                 Position of                                                                Ex.                                                                              pyridyl group                                                                        R.sup.3             R.sup.4      R.sup.5   R.sup.6                                                                             Hue                __________________________________________________________________________    88 3      (CH.sub.2).sub.2 CN C.sub.2 H.sub.5                                                                            CH.sub.3  H     red                89 3      (CH.sub.2).sub.2 COOCH.sub.3                                                                      C.sub.2 H.sub.5                                                                            H         H     red                90 3      (CH.sub.2).sub.2 OH C.sub.4 H.sub.9                                                                            CH.sub.3  H     red                91 3      C.sub.2 H.sub.5     C.sub.2 H.sub.5                                                                            NHCOCH.sub.3                                                                            H     pink               92 3      (CH.sub.2).sub.2 OCOCH.sub.3                                                                       C.sub.2 H.sub.5                                                                           CH.sub.3  H     red                93 3      (CH.sub.2).sub.2 OCOCH.sub.3                                                                      (CH.sub.2).sub.2 OCOCH.sub.3                                                               H         H     red                94 3      C.sub.2 H.sub.5     C.sub.2 H.sub.5                                                                            H         H     red                95 3      (CH.sub.2).sub.2 OCH.sub.3                                                                        (CH.sub.2).sub.2 OCH.sub.3                                                                 H         H     red                96 3      (CH.sub.2).sub.2 OCOCH.sub.3                                                                      (CH.sub.2).sub.2 OCOCH.sub.3                                                               CH.sub.3  H     red                97 3      (CH.sub.2).sub.2Ph  (CH.sub.2).sub.2 CN                                                                        H         H     red                98 3      (CH.sub.2).sub.2 OCOC.sub.2 H.sub.5                                                               (CH.sub.2).sub.2 OC.sub.2 H.sub.5                                                          Cl        H     red                99 3      (CH.sub.2).sub.2 OCOC.sub.2 H.sub.5                                                               (CH.sub.2).sub.2 CN                                                                        H         H     red                100                                                                              3      (CH.sub.2).sub.2 CN CH.sub.2 CHCH.sub.2                                                                        H         H     red                101                                                                              3      (CH.sub.2).sub.2 OCOCH.sub.3                                                                      (CH.sub.2).sub.2 OCOCH.sub.3                                                               CH.sub.3  OCH.sub.3                                                                           violet             102                                                                              3      CH.sub.2 CHCH.sub.2 CH.sub.2 CHCH.sub.2                                                                        NHCOCH.sub.3                                                                            OCH.sub.3                                                                           bluish                                                                        violet             103                                                                              3      (CH.sub.2).sub.2 COO(CH.sub.2).sub.2 OC.sub.2 H.sub.5                                             C.sub.2 H.sub.5                                                                            H         H     red                104                                                                              4      (CH.sub.2).sub.2 CN C.sub.2 H.sub.5                                                                            CH.sub.3  H     red                105                                                                              4      CH.sub.2Ph          (CH.sub.2).sub.2 COOCH.sub.3                                                               H         H     red                106                                                                              4      C.sub.2 H.sub.5     C.sub.2 H.sub.5                                                                            H         H     red                107                                                                              2      (CH.sub.2).sub.2 CN C.sub.2 H.sub.5                                                                            H         H     red                __________________________________________________________________________

                  TABLE 7a                                                        ______________________________________                                         ##STR17##                    IIIc                                                  Position of                                                             Ex.   pyridyl group                                                                             R.sup.8      Hue                                            ______________________________________                                        108   3           Cyclohexyl   yellowish orange                               109   3           Ph           yellowish orange                               110   3           Fur-2-ylmethyl                                                                             yellowish orange                               111   4           Ph           yellowish orange                               112   4           CH.sub.2Ph   yellowish orange                               ______________________________________                                    

                                      TABLE 8a                                    __________________________________________________________________________     ##STR18##                                                  IIId              Ex.                                                                              R.sup.3'           R.sup.3           R.sup.4            Hue                __________________________________________________________________________    113                                                                              H                  H                 (CH.sub.2).sub.3 O(CH.sub.2).sub.2                                             OCH.sub.3         reddish                                                                       orange             114                                                                              H                  H                 (CH.sub.2).sub.3 O(CH.sub.2).sub.2                                             OC.sub.2 H.sub.5  reddish                                                                       orange             115                                                                              H                  H                 (CH.sub.2).sub.3 O[(CH.sub.2).sub.                                            2 O].sub.2 C.sub.2 H.sub.5                                                                       reddish                                                                       orange             116                                                                              H                  H                 (CH.sub.2).sub.3 O(CH.sub.2).sub.4                                             O COCH.sub.3      reddish                                                                       orange             117                                                                              (CH.sub.2).sub.3 OCH.sub.3                                                                       (CH.sub.2).sub.2 OCH.sub.3                                                                      (CH.sub.2).sub.2 OCH.sub.3                                                                       red                118                                                                              CH(C.sub.2 H.sub.5)CH.sub.2 OCOCH.sub.3                                                          (CH.sub.2).sub.2 OCH.sub.3                                                                      (CH.sub.2).sub.2 OCH.sub.3                                                                       red                119                                                                              (CH.sub.2).sub.3 OCH.sub.3                                                                       (CH.sub.2).sub.2 OCOCH.sub.3                                                                    C.sub.2 H.sub.5    red                120                                                                              (CH.sub.2).sub.3 O(CH.sub.2).sub.2 OCH.sub.3                                                     H                 H                  reddish                                                                       orange             121                                                                              (CH.sub.2).sub.3 O[(CH.sub.2).sub.2 O].sub.2 C.sub.2 H.sub.5                                     H                 H                  reddish                                                                       orange             122                                                                              (CH.sub.2).sub.3 O[(CH.sub.2).sub.2 O].sub.2 C.sub.2 H.sub.5                                     (CH.sub.2).sub.3 OCH.sub.3                                                                      H                  red                123                                                                              (CH.sub.2).sub.3 O[(CH.sub.2 ).sub.2 O].sub.2 CH.sub.3                                           Ph                H                  red                124                                                                              (CH.sub.2).sub.3 O[(CH.sub.2).sub.2 O].sub.2 CH.sub.3                                            Ph-2-OCH.sub.3    H                  red                125                                                                              C.sub.2 H.sub.5    (CH.sub.2).sub.3 O[(CH.sub.2).sub.2 O].sub.2                                  CH.sub.3          C.sub.4 H.sub.9    pink               126                                                                              C.sub.2 H.sub.5    (CH.sub.2).sub.3 O(CH.sub.2).sub.4 OH                                                           H                  red                127                                                                              (CH.sub.2).sub.2 OCH.sub.3                                                                       (CH.sub.2).sub.3 O(CH.sub.2).sub.4 OH                                                           C.sub.2 H.sub.5    pink               128                                                                              (CH.sub.2).sub.3 OCH.sub.3                                                                       (CH.sub.2).sub.3 O(CH.sub.2).sub.4 OH                                                           H                  red                129                                                                              (CH.sub.2).sub.3 OCOCH.sub.3                                                                     (CH.sub.2).sub.3 O(CH.sub.2).sub.2 OC.sub.2                                                     H.sub.5            red                __________________________________________________________________________

                                      TABLE 9a                                    __________________________________________________________________________     ##STR19##                                                                    Ex.                                                                              Position of pyridyl group                                                                  R.sup.3       R.sup.5   Hue                                   __________________________________________________________________________    130                                                                              3            C.sub.3 H.sub.7                                                                             H         violet                                131                                                                              3            C.sub.2 H.sub.5                                                                             CH.sub.3  violet                                132                                                                              3            C.sub.4 H.sub.9                                                                             NHCOCH.sub.3                                                                            violet                                133                                                                              3            (CH.sub.2).sub.2 OC.sub.4 H.sub.9                                                           NHCOCH.sub.3                                                                            violet                                134                                                                              2            C.sub.6 H.sub.13                                                                            CH.sub.3  violet                                135                                                                              3            (CH.sub.2).sub.2 COOC.sub.7 H.sub.15                                                        NHCOCH.sub.3                                                                            violet                                136                                                                              3            (CH.sub.2).sub.2 OCOC.sub.6 H.sub.13                                                        NHCOCH.sub.3                                                                            violet                                137                                                                              3            (CH.sub.2).sub.4 CH(CH.sub.3)C.sub.2 H.sub.5                                                CH.sub.3  violet                                138                                                                              3            C.sub.3 H.sub.7                                                                             OCH.sub.3 violet                                139                                                                              3            [(CH.sub.2).sub.2 O].sub.2 C.sub.4 H.sub.9                                                  NHCOCH.sub.3                                                                            violet                                140                                                                              3            (CH.sub.2).sub.4 OH                                                                         NHCOCH.sub.3                                                                            violet                                141                                                                              3            (CH.sub.2).sub.2 OH                                                                         CH.sub.3  violet                                142                                                                              2            (CH.sub.2).sub.2 CN                                                                         NHCOC.sub.4 H.sub.9                                                                     violet                                143                                                                              3            C.sub.4 H.sub.9                                                                             H         violet                                144                                                                              3            C.sub.7 H.sub.15                                                                            H         violet                                145                                                                              3            H             H         violet                                146                                                                              2            H             CH.sub.3  violet                                147                                                                              3            H             C.sub.2 H.sub.5                                                                         violet                                __________________________________________________________________________

                  TABLE 1b                                                        ______________________________________                                        THERMOTRANSFER DATA RELATING TO TABLE 1a                                       Example  B          T*[°C.]                                                                        ##STR20##                                        ______________________________________                                         1       EC         82      16                                                 2       EC         93      14                                                 3       EC         100     15                                                 4       EC         90      17                                                 5       EC         80      16                                                 6       EC         82      17                                                 7       EC         86      17                                                 8       EC         89      19                                                 9       EC         80      23                                                10       EC         90      16                                                11       EC         98      15                                                12       EHE        96      19                                                13       CA         100     19                                                14       EC         102     21                                                15       EHE        98      19                                                16       EC         91      18                                                17       EC         93      20                                                18       EC         95      16                                                19       EC         92      17                                                20       EC         95      16                                                21       CA         93      12                                                22       MIX        96      13                                                23       MIX        97      15                                                24       MIX        101     17                                                25       MIX        99      19                                                26       MIX        88      18                                                27       MIX        91      19                                                28       MIX        93      17                                                29       MIX        85      19                                                30       MIX        94      18                                                31       EC         90      16                                                32       EHE        90      20                                                ______________________________________                                    

                  TABLE 2b                                                        ______________________________________                                        THERMOTRANSFER DATA RELATING TO TABLE 2a                                       Example  B          T*[°C.]                                                                        ##STR21##                                        ______________________________________                                        33       MIX        97      13                                                34       EHE        88      17                                                35       CA         99      16                                                36       MIX        99      19                                                37       MIX        99      19                                                38       MIX        89      21                                                39       MIX        88      19                                                40       MIX        99      17                                                41       MIX        86      16                                                ______________________________________                                    

                  TABLE 3b                                                        ______________________________________                                        THERMOTRANSFER DATA RELATING TO TABLE 3a                                       Example  B          T*[°C.]                                                                        ##STR22##                                        ______________________________________                                        42       EC         106     16                                                43       EC         98      17                                                44       EHE        80      20                                                45       CA         94      19                                                46       EC         93      11                                                47       EC         82      12                                                48       EC         91      16                                                49       EC         98      17                                                50       EC         85      18                                                51       EC         99      19                                                52       EC         96      17                                                53       MIX        97      19                                                54       MIX        93      18                                                55       MIX        100     19                                                56       MIX        100     18                                                57       MIX        99      19                                                58       MIX        89      13                                                59       EC         99      19                                                60       EC         88      19                                                61       MIX        99      20                                                62       EC         86      16                                                63       EHE        94      22                                                64       MIX        83      14                                                65       MIX        104     20                                                66       MIX        99      17                                                67       MIX        79      20                                                68       EC         99      13                                                69       EC         88       2                                                ______________________________________                                    

                  TABLE 4b                                                        ______________________________________                                        THERMOTRANSFER DATA RELATING TO TABLE 4a                                       Example  B          T*[°C.]                                                                        ##STR23##                                        ______________________________________                                        70       EC         93      17                                                71       MIX        99      15                                                72       MIX        88      12                                                ______________________________________                                    

                  TABLE 5b                                                        ______________________________________                                        THERMOTRANSFER DATA RELATING TO TABLE 5a                                       Example  B          T*[°C.]                                                                        ##STR24##                                        ______________________________________                                        73       MIX        97      21                                                74       MIX        95      19                                                75       EC         96      18                                                76       EHE        93      17                                                77       MIX        110     16                                                78       MIX        99      15                                                79       EC         106     20                                                80       MIX        99      21                                                81       CA         98      22                                                82       MIX        96      19                                                83       MIX        84      22                                                84       EC         94      13                                                85       EHE        90      14                                                86       MIX        99      17                                                87       EC         99      16                                                ______________________________________                                    

                  TABLE 6b                                                        ______________________________________                                        THERMOTRANSFER DATA RELATING TO TABLE 6a                                       Example  B          T*[°C.]                                                                        ##STR25##                                        ______________________________________                                         88      MIX        89      16                                                 89      MIX        89      20                                                 90      MIX        99      19                                                 91      MIX        98      20                                                 92      MIX        99      19                                                 93      MIX        96      18                                                 94      MIX        99      22                                                 95      MIX        98      19                                                 96      MIX        80      18                                                 97      MIX        99      22                                                 98      MIX        89      19                                                 99      MIX        99      18                                                100      MIX        109     17                                                101      MIX        107     16                                                102      MIX        96      21                                                103      MIX        89      19                                                104      MIX        98      18                                                105      MIX        84      17                                                106      MIX        94      19                                                107      MIX        95      14                                                ______________________________________                                    

                  TABLE 7b                                                        ______________________________________                                        THERMOTRANSFER DATA RELATING TO TABLE 7a                                       Example  B          T*[°C.]                                                                        ##STR26##                                        ______________________________________                                        108      MIX        98      15                                                109      MIX        97      19                                                110      MIX        96      21                                                111      MIX        95      17                                                112      MIX        93      19                                                ______________________________________                                    

                  TABLE 8b                                                        ______________________________________                                        THERMOTRANSFER DATA RELATING TO TABLE 8a                                       Example  B          T*[°C.]                                                                        ##STR27##                                        ______________________________________                                        113      MIX        99      17                                                114      MIX        99      16                                                115      MIX        89      19                                                116      MIX        97      19                                                117      MIX        86      18                                                118      MIX        99      17                                                119      MIX        98      16                                                120      MIX        95      15                                                121      MIX        97      19                                                122      MIX        96      18                                                123      MIX        99      14                                                124      MIX        98      19                                                125      MIX        85      13                                                126      MIX        101     19                                                127      MIX        98      18                                                128      MIX        87      17                                                129      MIX        96      20                                                ______________________________________                                    

                  TABLE 9b                                                        ______________________________________                                        THERMOTRANSFER DATA RELATING TO TABLE 9a                                       Example  B          T*[°C.]                                                                        ##STR28##                                        ______________________________________                                        130      EC         88      15                                                131      MIX        97      16                                                132      MIX        97      17                                                133      MIX        96      19                                                134      EC         98      17                                                135      EC         89      22                                                136      EHE        95      17                                                137      MIX        104     18                                                138      MIX        98      19                                                139      MIX        89      18                                                140      MIX        97      16                                                141      MIX        96      13                                                142      MIX        95      14                                                143      MIX        92      17                                                144      MIX        90      18                                                145      MIX        111     19                                                146      MIX        89      18                                                147      MIX        98      19                                                ______________________________________                                    

We claim:
 1. A process for transferring an azo dye by diffusion from atransfer to a plastic-coated substrate with the aid of a heat source,which comprises using for this purpose a transfer on which there is orare situated one or more azo dyes of the formula I ##STR29## in whichthe substituents have the following meanings: X is a radical of theformula IIa or IIb ##STR30## where R¹ is hydrogen, C₁ -C₆ -alkyl, orphenyl which may be substituted by C₁ -C₄ -alkyl, C₁ -C₂ -alkoxy,chlorine, bromine or cyano,n is 1 or 2, and R² is hydrogen, C₁ -C₄-alkyl, C₁ -C₄ -alkoxy, chlorine or bromine, and K is the radical of acoupling component III

    H--K                                                       III

of an aniline, aminoaphthaline, pyrazole, hydroxypyridone ortetrahydroquinoline.
 2. A process as claimed in claim 1, wherein K isof:aniline derivatives of formula IIIa ##STR31## aminoaphthalinederivatives of the formula IIIb ##STR32## pyrazole derivatives of theformula IIIc ##STR33## hydroxypyridone derivatives of the formula IIIe##STR34## tetrahydroquinoline derivatives of the formula IIIf ##STR35##wherein R³ and R⁴ are each hydrogen; C₁ -C₁₀ -alkyl whose carbon chainmay be interrupted by from one to three oxygen atoms in ether functionand which may bear the following substituents: cyano, hydroxyl, phenyl,phenoxy, phenylaminocarbonyloxy, benzyloxy, benzoyloxy, which may haveC₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, fluorine, chlorine or bromine assubstituents, C₁ -C₄ -alkanoyloxy, C₁ -C₆ -alkoxycarbonyloxy, C₁ -C₈-alkoxycarbonyl, mono- or di-C₁ -C₈ -alkylaminocarbonyloxy, in the lastthree of which the carbon chain may be interrupted by one or two oxygenatoms in ether function;C₃ -C₅ -alkenyl or C₅ -C₇ -cycloalkyl; phenylwhich may be substituted by C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, C₁ -C₄-dialkylamino, acetylamino, fluorine, chlorine or bromine; R⁵ ishydrogen; chlorine;C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, C₁ -C₄ -alkanoylamino,which may have C₁ -C₄ -alkoxy, phenoxy or chlorine as substituents, C₂-C₃ -alkenoylamino, benzoylamino, ureido, mono- or di-C₁ -C₄-alkylureido or C₁ -C₄ -alkylsulfonylamino; R⁶ is hydrogen, chlorine, C₁-C₄ -alkyl or C₁ -C₄ -alkoxy; R⁷ is hydrogen, C₁ -C₈ -alkyl or phenyl;R⁸ is hydrogen, C₁ -C₈ -alkyl, which may have phenyl, furyl or thienylas substituents, C₅ -C₇ -cycloalkyl or phenyl.
 3. A process fortransferring an azo dye by diffusion from a transfer to a plastic-coatedsubstrate with the aid of a heat source, which comprises using for thispurpose of transfer on which there is or are situated one or more azodyes of the formula I ##STR36## in which the substituents have thefollowing meanings: X is a radical of the formula IIb ##STR37## where R²is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, chlorine or bromine, andK isthe radical of a coupling component III

    H--K                                                       III

of an aniline, aminoaphthaline, pyrazole, diaminopyridine,hydroxypyridone or tetrahydroquinoline.
 4. A process as claimed in claim3, wherein K is of:aniline derivatives of formula IIIa ##STR38##aminoaphthaline derivatives of the formula IIIb ##STR39## pyrazolederivatives of the formula IIIc ##STR40## diaminopyridine derivatives ofthe formula IIId ##STR41## hydroxypyridone derivatives of the formulaIIIe ##STR42## tetrahydroquinoline derivatives of the formula IIIf##STR43## wherein R³, R^(3'), R⁴ and R^(4') are each hydrogen; C₁ -C₁₀-alkyl whose carbon chain may be interrupted by from one to three oxygenatoms in ether function and which may bear the following substituents:cyano, hydroxyl, phenyl, phenoxy, phenylaminocarbonyloxy, benzyloxy,benzoyloxy, which may have C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy, fluorine,chlorine or bromine as substituents, C₁ -C₄ -alkanoyloxy, C₁ -C₈-alkoxycarbonyloxy, C₁ -C₈ -alkoxycarbonyl, mono- or di-C₁ -C₈-alkylaminocarbonyloxy, in the last three of which the carbon chain maybe interrupted by one or two oxygen atoms in ether function;C₃ -C₅-alkenyl or C₅ -C₇ -cycloalkyl; phenyl which may be substituted by C₁-C₄ -alkyl, C₁ -C₄ -alkoxy, C₁ -C₄ -dialkylamino, acetylamino, fluorine,chlorine or bromine; R⁵ is hydrogen; chlorine;C₁ -C₄ -alkyl, C₁ -C₄-alkoxy, C₁ -C₄ -alkanoylamino, which may have C₁ -C₄ -alkoxy, phenoxyor chlorine as substituents, C₂ -C₃ -alkenoylamino, benzoylamino,ureido, mono- or di-C₁ -C₄ -alkylureido or C₁ -C₄ -alkylsulfonylamino;R⁶ is hydrogen, chlorine, C₁ -C₄ -alkyl or C₁ -C₄ -alkoxy; R⁷ ishydrogen, C₁ -C₈ -alkyl or phenyl; R⁸ is hydrogen, C₁ -C₈ -alkyl, whichmay have phenyl, furyl or thienyl as substituents, C₅ -C₇ -cycloalkyl orphenyl.
 5. A process as claimed in claim 1, wherein the heat source is athermal printing head.
 6. A process as claimed in claim 3, wherein theheat source is a thermal printing head.